1. Field of the Invention
The invention relates generally to an optical oscillator with milimeterwave frequency. More particularly, it relates to an optical oscillator with milimeterwave frequency having a 8-character shape optical fiber resonator structure in which a line polarizer is inserted so that the non-linear property of the 8-character shape optical fiber resonator can be employed with a specific modification of a ring type optical fiber resonator, whereby two laser modes are modulated to be an ultra-high frequency of 60, 120 and 160 GHz due to Magnolia phenomenon between the two laser modes.
2. Description of the Prior Art
In the milimeterwave communication system which has a large information capacity for four-generation wireless internet service, a method of using a semiconductor high frequency optical modulator and a modulation method of a resonator itself has been proposed for recent 5xcx9c6 years, as a method of connecting a milimeterwave oscillator to the base stations.
In the optical modulator mode, however, the frequency region is limited to up to 30 GHz, the maximum. And the modulating method employs the optical fiber resonator of a dual ring structure of 40 GHz region shown in FIG. 1.
FIG. 1 shows a frequency variable laser source having a dual ring type resonator structure. One of the two ring type resonators includes a WDM coupler 10 for coupling the pump light of 980 nm, an optical amplification optical fiber (LAF) 10 of 10 m for amplifying the light, a dispersion-compensating optical fiber 12 20 m for a non-linear polarizing effect, an optical direction indicator 13, and a first polarization controller 14. The other of the two-ring type resonator includes a dispersion-compensating optical fiber 18 of 15 m for a non-linear polarization effect, and a second polarization controller 16. These ring type resonators are coupled by the optical fiber coupler and produces an output light by means of a 10% coupler.
The present invention is contrived to solve the above problems and an object of the present invention is to provide a good optical oscillator having a high modulating frequency of 60, 120 and 160 GHz that could not be produced through commercial components.
Another object of the present invention is to provide a high frequency laser optical oscillator having a simple structure without using expensive components such as an optical modulator.
Laser is oscillated in a wavelength in which the gain is maximized during one period of resonance within a single laser resonator. In an 8-character shape optical fiber resonator, a factor of determining the gain further includes a non-linear characteristic generated at an asymmetric optical path as well as the gain at the optical amplification medium and a birefringence phenomenon against the polarization mode of a laser existing within the optical fiber. Due to the non-linear phenomenon, an ultra-short wave pulse, wavelength variable continuous light source and ultra-high frequency modulated light source in which their characteristics of the light source are below 1 ps can be fabricated depending on the structure of the optical components. In the present invention, a line polarizer is inserted into an 8 character shape optical fiber resonator in which a single ring type resonator is divided into two circuits by dividing it into a 50% optical fiber coupler in order to oscillate the laser mode in dual. Thus, a laser light source that is modulated to be an ultra-high frequency of 60, 120 and 160 GHz by means of Magnolia phenomenon between the two laser modes can be provided
The present invention employs a phenomenon in which two lights separately outputted from the coupler of the linear circuit and the non-linear circuit are experienced by different refractive index that exist asymmetrically. Under special conditions that are selected by the line polarizer into which a light source oscillating in a single mode is inserted. In case that the linear polarizer does not exist, the dual mode satisfying the two resonating conditions are oscillated so that a modulated frequency high frequency laser is produced. Further, the modulating frequency of laser oscillated by the polarizing controller is converted into two types using the specific condition depends on the refractive index.
An optical oscillator with milimeterwave frequency according to the present invention is characterized in that it comprises a wavelength coupler for receiving a pump light, an optical amplification optical fiber for amplifying the light from the wavelength coupler, a dispersion-compensating optical fiber for obtaining a non-linear polarizing effect of the light transmitted via the optical amplification optical fiber, a line polarizer for varying the wavelength of the light having a non-linear polarizing effect by means of the dispersion-compensating optical fiber, and a polarizing controller for controlling the modulating frequency of the light transmitted via the line polarizer; an output circuit having an optical direction indicator for precluding the path of the light, a 10% optical fiber coupler for output light, and a dispersion-compensating optical fiber for determining the wavelength region; and an optical coupler for connecting the non-linear circuit and the output circuit.